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Morphology of a specimen of Supersaurus (Dinosauria, Sauropoda) from the Morrison Formation of Wyoming, and a re-evaluation of diplodocid phylogeny


Abstract and Figures

A new specimen of Supersaurus vivianae is described, providing additional information about the osteology of Supersaurus. The single Supersaurus individual that the WDC quarry produced allows a re- examination of elements referred to Supersaurus from the Dry Mesa quarry. The osteology supports maintaining the generic distinction of Supersaurus. Phylogenetic evaluation finds a monophyletic Apatosaurinae containing (Apatosaurus + Supersaurus) + Suuwassea, and a monophyletic Diplodocinae containing (Diplodocus + Seismosaurus) + Barosaurus, although the generic distinction of Seismosaurus is not supported in the current analysis. RESUMO: Morfologia de um espécime de Supersaurus (Dinosauria, Sauropoda) da Formação Morrison de Wyoming e uma reavaliação da filogenia de diplodocídeos. Um novo espécime de Supersaurus vivianae é descrito, acrescentando informações sobre a osteologia de Supersaurus. O único indivíduo de Supersaurus coletado no afloramento WDC permite o re-exame dos elementos referidos a Supersaurus do afloramento de Dry Mesa. A osteologia suporta a manutenção da distinção genérica de Supersaurus. Uma avaliação filogenética resultou em um grupo monofilético Apatosaurinae contendo (Apatosaurus + Supersaurus) + Suuwassea, e um grupo monofilético Diplodocinae contendo (Diplodocus + Seismosaurus) + Barosaurus, embora a distinção genérica de Seismosaurus não esteja suportada na presente análise.
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1 Submitted on September 14, 2006. Accepted on November 16, 2007.
2 University of Wyoming, School of Arts and Sciences, Laramie, Wyoming, 82071, U.S.A. E-mail:
3 Big Horn Basin Foundation, 110 Carter Ranch Road, Thermopolis, Wyoming, 82443, U.S.A.
4 The Wyoming Dinosaur Center, 110 Carter Ranch Road, Thermopolis, Wyoming, 82443, U.S.A.
Arquivos do Museu Nacional, Rio de Janeiro, v.65, n.4, p.527-544, out./dez.2007
ISSN 0365-4508
(With 15 figures)
ABSTRACT: A new specimen of Supersaurus vivianae is described, providing additional information about
the osteology of Supersaurus. The single Supersaurus individual that the WDC quarry produced allows a re-
examination of elements referred to Supersaurus from the Dry Mesa quarry. The osteology supports
maintaining the generic distinction of Supersaurus. Phylogenetic evaluation finds a monophyletic
Apatosaurinae containing [Apatosaurus + Supersaurus] + Suuwassea, and a monophyletic Diplodocinae
containing [Diplodocus + Seismosaurus] + Barosaurus, although the generic distinction of Seismosaurus is
not supported in the current analysis.
Key words: Dinosauria. Sauropoda. Supersaurus. Phylogeny. Morrison Formation.
RESUMO: Morfologia de um espécime de Supersaurus (Dinosauria, Sauropoda) da Formação Morrison de
Wyoming e uma reavaliação da filogenia de diplodocídeos.
Um novo espécime de Supersaurus vivianae é descrito, acrescentando informações sobre a osteologia de
Supersaurus. O único indivíduo de Supersaurus coletado no afloramento WDC permite o re-exame dos
elementos referidos a Supersaurus do afloramento de Dry Mesa. A osteologia suporta a manutenção da
distinção genérica de Supersaurus. Uma avaliação filogenética resultou em um grupo monofilético
Apatosaurinae contendo [Apatosaurus + Supersaurus] + Suuwassea, e um grupo monofilético Diplodocinae
contendo [Diplodocus + Seismosaurus] + Barosaurus, embora a distinção genérica de Seismosaurus não
esteja suportada na presente análise.
Palavras-chave: Dinosauria. Sauropoda. Supersaurus. Filogenia. Formação Morrison.
Diplodocoid taxa rank among the earliest described
and best-known sauropods (M
, 1896; H
1901; H
, 1906; L
, 1919; G
, 1936),
with new taxa continuing to be described, such as
Suuwassea (H
& D
, 2004) and
Dinheirosaurus (B
& M
, 1999). Recent
studies have provided needed attention to
diplodocoid phylogenetic systematics (U
al., 2004; T
& N
, 2005; M
, 2005;
, 2006), yet several diplodocid taxa have
remained problematic due to their fragmentary
nature, notably Seismosaurus and Supersaurus.
In 1985, J.A. Jensen erected three sauropod genera
based on material collected from Dry Mesa Quarry:
Ultrasauros macintoshi; Dystylosaurus edwini; and
Supersaurus vivianae. All three have had complex
nomenclatural histories (e.g., J
, 1987; C
1995; C
et al., 1996; C
& S
2001), with the types of both Ultrasauros and
Dystylosaurus eventually sunk into Supersaurus
vivianae (C
, 1995; C
& S
, 2001).
In addition, some of the specimen numbers have
changed in the last two decades.
The name Supersaurus was erected for a single
scapulocoracoid, BYU 12962 (J
, 1985).
Dozens of elements have been referred to this taxon
since. Some referrals, such as the matching right
scapulocoracoid, are unambiguous. Other elements
have been referred based on quarry location,
relative size, and hypotheses of phylogenetic
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position. The depositional circumstances and
multiple disarticulated sauropod taxa in the Dry
Mesa quarry made unambiguous referrals of other
elements difficult. As a result, Supersaurus has
largely been excluded from phylogenetic analyses,
and opinion on its generic validity has been mixed.
At one time J.S. McIntosh thought S. vivianae was
a large species of Barosaurus, but more recently
supported generic distinction (MCINTOSH, 2005;
GLUT, 1997). Alternately, it has been suggested that
Supersaurus should be synonymized with
Seismosaurus, or that the genus is a nomen dubium
(GILLETTE, 1994).
A second specimen, a single individual from a
quarry in Wyoming, makes it possible to evaluate
the taxonomic status of referred supersaur skeletal
elements in the BYU collection. Combined with
morphological data from WDC DMJ-021 it is now
possible to provide an emended diagnosis of the
species, and to add Supersaurus to existing
phylogenetic analyses. Approximately 30% of the
skeleton has been recovered of WDC DMJ-021
which combined with the BYU specimen yields
knowledge of 45-50% of the osteology of
Abbreviations: Institutional. AMNH, American
Museum of Natural History, New York, New York;
BYU, Brigham Young University, Provo, Utah;
CM, Carnegie Museum of Natural History,
Pittsburgh, Pennsylvania; DMJ, Douglas
Morrison Jimbo site; DMNH, Denver Museum of
Nature and Science, Denver, Colorado; NMMNH,
New Mexico Museum of Natural History and
Science, Albuquerque, New Mexico; NSMT,
National Science Museum, Tokyo, Japan; UWGM,
University of Wyoming Geological Museum,
Laramie, Wyoming; WDC, Wyoming Dinosaur
Center, Thermopolis, Wyoming; YPM, Yale
Peabody Museum, New Haven, Connecticut.
A single individual (WDC DMJ-021) with
approximately 30% of the skeleton was discovered
in the Morrison Formation near Douglas Wyoming.
The specimen includes a relatively complete
presacral column, sacral fragments, and
incomplete caudal series. Remains of costal
elements, fragmentary pelvic and femur, and
complete tibiae and fibulae were also recovered.
Elements previously referred to this taxon were also
analysed. We follow CURTICE et al. (1996) in using
current BYU specimen numbers, with original
numbers noted when necessary for continuity with
earlier publications (Tab. 1).
A phylogenetic analysis was conducted using a
modified version of HARRIS & DODSON’s (2004) data
matrix. The data set was modified by the addition
of Supersaurus and Seismosaurus (see Appendix 1
for character scoring), as well as four new
characters (Appendix 2), in part in an attempt to
distinguish Seismosaurus from Diplodocus.
WDC DMJ-021 was found in the Morrison
Formation near Douglas Wyoming (Fig.1).
Taphonomy of the Jimbo Quarry is interpreted as
a debris-flow deposit that buried a single sauropod
skeleton (LOVELACE et al., 2003, LOVELACE, 2004;
LOVELACE, 2006). While allocthanous in nature, the
debris flow appears to have preserved an
autochthanous burial of the specimen, prior to the
mass wasting event (LOVELACE, 2006). The
taphonomic interpretation of a single individual is
backed up by relative size of preserved elements,
and the absence of duplicate elements.
SAURISCHIA Seeley, 1887
SAUROPODA Marsh, 1878
APATOSAURINAE Janensch, 1929
Supersaurus vivianae Jensen, 1985
Holotype – BYU 12962 JENSEN (1985), a large
diplodocid left scapulocoracoid.
Referred specimens – BYU 4839, BYU 9024, BYU
9044, BYU 9045, BYU 9085, BYU 10612, BYU
12424, BYU 12555, BYU 12639, BYU 12819, BYU
12861, BYU 12946, BYU 12962, BYU 13016, BYU
13018, BYU 13981, BYU 16679, BYU 17462; Dry
Mesa specimens likely pertaining to the type
individual. Remains include a nearly complete
pelvic girdle and sacrum, a right scapulocoracoid,
several axial elements from the cervical, dorsal, and
caudal region (see Tab.1 for element identification).
WDC DMJ-021, a single associated specimen
including a relatively complete presacral column
Arq. Mus. Nac., Rio de Janeiro, v.65, n.4, p.527-544, out./dez.2007
(portions of 10 cervical vertebrae and 5 dorsal
vertebrae), sacral fragments, and representative but
incomplete caudal series. Several costal elements,
fragmentary pelvic and femoral remains, and
complete tibiae and fibulae. While a scapula is not
known for WDC DMJ-021, other elements are
identical to axial elements referred to the type
individual of Supersaurus.
TABLE 1. Status of Dry Mesa Quarry specimens referred to Supersaurus. “Specimen #” column reflects current
BYU ascension numbers; “Element” column provides a brief description of element; “Interpreted Referral Status”
column provides current status on taxonomic referral.
(1 JENSEN, 1985; 2 JENSEN, 1987; 3 CURTICE & CURTICE, 1996; 4 CURTICE et al., 1996; 5 CURTICE & STADTMAN,
2001) – 6CURTICE, 1996.
BYU 90251 left scapulocoracoid; (holotype) N/A
BYU 129621 right scapulocoracoid Yes; mate to BYU 9025
BYU 129461 right ischium Yes; verified by WDC DMJ-021
BYU 128546 distal proximal caudal No; reassigned in this paper to Diplodocinae
BYU 128431,5 distal proximal caudal No; reassigned in this paper to Diplodocinae
BYU 90841 12 articulated mid-caudals No; reassigned in this paper to Diplodocinae
BYU 90771 mid-caudal vertebra No; reassigned in this paper to Diplodocinae
BYU 90242 mid-cervical vertebra Yes; verified by WDC DMJ-021
BYU 90453,5 proximal caudal vertebra Yes; verified by WDC DMJ-021
BYU 90443;4 posterior dorsal vertebra Yes; verified by WDC DMJ-021
BYU 123905 Carpal Indeterminate
BYU 90005 Phalanx Indeterminate
BYU 137445 left ulna No; 20-25% larger than predicted by length of
tibia for WDC DMJ-021
BYU 125555 left ischium Yes; mate to BYU 12946
BYU 124245 right pubis Yes; verified by WDC DMJ-021
BYU 48395 caudal vertebra Fragmentary; CURTICE (1996) suggests it is
BYU 126395 caudal vertebra Yes; not verified by WDC DMJ-021
BYU 128195 caudal vertebra Yes; verified by WDC DMJ-021
BYU 128145 dorsal vertebra Unable to confirm
BYU 9192 caudal vertebra Unable to confirm
BYU 130185 pelvis (left illium/four sacral vertebra) Yes; not verified by WDC DMJ-021
BYU 13981 mid caudal vertebra Referred to Supersaurus in the text
BYU 13016 mid caudal vertebra Referred to Supersaurus in the text
BYU 12861 mid caudal vertebra Referred to Supersaurus in the text
BYU 10612 mid caudal vertebra Referred to Supersaurus in the text
BYU 9085 mid caudal vertebra Referred to Supersaurus in the text
BYU 17462 anterior caudal vertebra Referred to Supersaurus in the text
BYU 45035 dorsal vertebra Yes; verified by WDC DMJ-021
BYU 16679 caudal vertebra Referred to Supersaurus in the text
Arq. Mus. Nac., Rio de Janeiro, v.65, n.4, p.527-544, out./dez.2007
Referral of all material is supported by relative
position within their respective quarries (CURTICE &
STADTMAN, 2001; LOVELACE, 2006), size of the skeletal
elements, and congruence of phylogenetically
significant diplodocid characters between the
scapula and referred material (see below).
Emended Diagnosis – Large diplodocid sauropod
with the following characteristics: elongate cervical
vertebrae (elongation index ranging from 4-7) with
an a extreme narrowing of the ventral surface of
the vertebral body at midlength; well-developed
parallel keels on the ventral surface of the cervical
series; small ventral pleurocoel located between the
parapophyses with dual pneumatopores divided by
an anterior-posteriorly directed septa; lateral
pleurocoels simple, shallow depressions with small
pneumatopores; posterior dorsals with
proportionately tall neural spines (> than 0.5 of
vertebral height) and reduced neural arch height;
anterior dorsals with dorsal vertebral bodies with
moderate midline keel and shallow lateral sulci;
posterior dorsals opisthocoelous; anterior caudal
vertebrae with prominent ventral keel, and shallow
pleurocoels; ribs pneumatized, with anterior-
posteriorly expanded shafts; scapular blade
expanded dorsally; deltoid ridge perpendicular to
the acromian ridge.
Cervical vertebrae – The cervical vertebrae of S.
vivianae are extremely elongate (length of centra for
BYU 9024 is 1380mm). Centra length exceeds even
those of Sauroposeidon, which was reported as
having the longest cervical vertebrae of any known
sauropod (WEDEL et al., 2000); the greatest centra
measurement of Sauroposeidon is 1250mm. While
no cervical vertebra is complete, preserved elements
are adequate for description and comparison.
Supersaur cervical vertebral autapomorphies
include a mediolaterally narrow ventral surface (5-
8cm) of the middle centra. Cervical vertebrae lack
elaborate pneumatic fossae (pleurocoels), a feature
noted by JENSEN (1985) as differing greatly from the
condition typically seen in the Diplodocidae. Cervical
ribs are sub-equal in length to their respective
centra, with some extending slightly beyond the
posterior limit of the cotyle.
A mid-cervical vertebra (BYU 9024; Fig.2) originally
assigned to Ultrasauros (JENSEN, 1985) was later
referred to the type individual by JENSEN (1987).
BYU 9024 compares favorably to preserved WDC
cervical vertebrae, supporting its referral to the type
Fig.1- The range of Morrison Formation (shaded) exposed throughout the Rocky Mountain region of western North America.
Modified after DUNAGAN & TURNER (2004).
Arq. Mus. Nac., Rio de Janeiro, v.65, n.4, p.527-544, out./dez.2007
individual. The WDC specimen includes substantial
portions of ten cervical vertebrae, representing most
of the cervical column. Seven of the cervical
vertebrae contain nearly complete centra, each over
a meter in length.
In cross section the form of the centra can be
generalized as an I-beam (Fig.3E). The diameter of
pneumatopores on the lateral surface of the centra
are no more than 30-80mm. This condition is
reduced in comparison to the pneumatopores in
several Apatosaurus, and contrasts greatly with the
elaborate pneumatic structures seen in the centra
of Diplodocus and Barosaurus (Fig.3). On the ventral
surface just posterior of the centroparapophyseal
lamina there are two pneumatopores separated by
a medial septum. This feature appears in all
cervicals where this area is preserved (both anterior
and posterior cervical vertebrae demonstrate this
condition). Figure 4 shows this condition in cervical
vertebrae (Cv.) 14 of Apatosaurus ajax as well as in
Cv.13 of Supersaurus; however this feature is
absent in Barosaurus (LULL, 1919) and Diplodocus.
More work is needed to determine the distribution
of this character in diplodocids.
Dorsal vertebrae – Five dorsal vertebrae have been
recovered for WDC DMJ-021; four vertebrae
preserve complete centra, one lacks only the
transverse processes, while two preserve isolated
neural spines. BYU 9044 exhibits features seen in
several of WDC dorsal vertebrae, supporting CURTICE
et al.’s (1996) referral to the same individual as the
type. WDC dorsal vertebra WDC DMJ-021-085 is
extremely similar to mid-anterior dorsal vertebrae
BYU 4503 (approximately number 4; CURTICE &
STADTMAN, 2001), supporting BYU 4503’s referral
to the Dry Mesa Supersaurus.
Supersaurus dorsal vertebrae demonstrate several
synapomorphic characters with Apatosaurus. The
neural spines (measured from the junction between
postzygapophyses to the top of the neural spine) of
the posterior dorsal vertebrae make up more than
half the height of the vertebra. This is similar to
the condition seen in Apatosaurus. Both Diplodocus
and Barosaurus exhibit posterior dorsal neural
spine heights that contribute to less than half of
the entire vertebrae (Fig.5). The bifed neural spines
are lost prior to dorsal seven, and possibly as early
as dorsal four or five (inferred from the merging of
the spinoprezygapophyseal laminae with the
prespinal lamina), unlike in Diplodocus. The cleft
in the posterior dorsal neural spines of Diplodocus
is absent in Supersaurus.
Preserved dorsal centra of Supersaurus exhibit a
ventral keel on the centra, as observed in
Apatosaurus (UWGM 15556). While the posterior
dorsal vertebrae of all other diplodocids are
amphiplatean (GILMORE, 1936; HATCHER, 1901; LULL,
1919), the posterior dorsals of both Supersaurus
specimens are opisthocoelous, a probable
autapomorphy of Supersaurus.
Fig.2- Cervical vertebrae 11 or 12, referred to type specimen of Supersaurus vivianae (BYU 9024).
Arq. Mus. Nac., Rio de Janeiro, v.65, n.4, p.527-544, out./dez.2007
Caudal vertebrae – CURTICE (1996) and MACINTOSH
(2005) suggest that diplodocid caudal vertebrae are
a useful source of taxonomically significant
characters. Supersaurus caudals share the
presence of pneumatic fossae with Barosaurus and
Diplodocus. Aside from this character, they exhibit
numerous apatosaurine synapomorphies. Relative
to diplodocines the anterior caudal vertebrae have
short (less than twice the height of the centra) and
distally expanded (rectangular box-like) neural
spines (Fig.6) that lack a bifed cleft. The centra are
heart-shaped in cross-section, have well-developed
anterior cotyles and a platyean posterior surface,
contrary to the condition reported by CURTICE (1995)
in which caudal vertebrae are reported as having a
pronounced posterior ball. Inspection shows
neither BYU 9045 nor WDC DMJ-021-083 exhibit
a pronounced posterior ball, nor do any other
caudals from either locality. We were unable to
confirm the presence of a hyposphene/hypantrum
complex on any of the BYU Supersaurus caudals,
nor is one present on WDC DMJ-021.
Anterior caudal vertebrae centra exhibit a
prominent ventral midline keel, as seen in
Apatosaurus excelsus (GILMORE, 1936). The keel
disappears by caudal vertebrae 12 or 13. Centra
length is subequal over the first 30 caudal
vertebrae, as in Apatosaurus. The height of the
caudal neural spines decreases rapidly from
anterior to posterior, a condition seen in both
Apatosaurus and Barosaurus, but unlike the very
slight decrease in anterior to posterior neural
spine height seen in Diplodocus and Seismosaurus
(see Figs.7-8).
Fig.3- Lateral views of cervical vertebrae from A, Diplodocus carnegii (HATCHER, 1901); B, Barosaurus lentus (LULL, 1919); C,
Apatosaurus louisae (GILMORE, 1936); D and E, Supersaurus vivianae; demonstrating pneumatic modifications of centra.
Supersaurus has the least amount of modification with minimal size for pneumatopores. Internal structure is similar to
that seen in other diplodocids (JANENSCH, 1947). Left lateral view of Cv.13 (D, missing the condyle, prezygapophyses and
neural spine; length of incomplete centra 94cm). E, cross section through Cv.11, 5cm posterior of the diapophysis.
Arq. Mus. Nac., Rio de Janeiro, v.65, n.4, p.527-544, out./dez.2007
Fig.4- Ventral views of posterior cervical centra from A, Supersaurus; B, Barosaurus lentus (LULL, 1919); and C, Apatosaurus
ajax (UPCHURCH et al., 2004). There are two pneumatopores along the midline of the centra slightly posterior to the
parapophyses, each pair separated by a sagital septum. This condition is seen in A. ajax as well as Supersaurus, but not
observed in Barosaurus (LULL, 1919) or DMNH 1494 Diplodocus.
Fig.5- Dorsal vertebrae (third pre-sacral for each species) scaled to the same height to demonstrate relative position of
the hyposphene on posterior dorsals. A, Supersaurus (WDC DMJ-021); B, Apatosaurus louisae (GILMORE, 1936); C,
Diplodocus (HATCHER, 1901); D, Barosaurus (LULL, 1919). The ratios (relative height of centra and neural arch to the
height of the neural spine) are 0.44, 0.40, 0.53, and 0.52 respectively, showing that diplodocines have a taller neural
arch relative to Supersaurus and Apatosaurus.
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The caudal vertebrae of S. vivianae are easily
distinguishable from the caudal vertebrae of
Diplodocus or Barosaurus. None of the WDC caudal
vertebrae demonstrate the classic diplodocine
ventral longitudinal hollow. Nor do the anterior
caudal vertebrae exhibit tall and narrow neural
spines with a deep cleft at the distal end, as in
Diplodocus and Seismosaurus.
We evaluated these characters in referred caudal
material in the BYU collections (Table 1). BYU
12854, 12843, 9084 (12 articulated mid caudal
vertebrae), and 9077 are incompatible with the
vertebrae found at the WDC site, and should be
reassigned to Diplodocinae incertae sedis based on
their well-developed ventral longitudinal hollow.
Based on size and morphological similarity with
WDC DMJ-021, BYU caudal vertebrae 12639,
13981, 13016, 12861, 10612, 9085, 17462, and
16679 can be confidently assigned to the type
individual of Supersaurus vivianae.
Ribs – MARSH (1896) figured pneumatic cavities
from a costal element of A. excelsus, and GILMORE
(1936) published an image and description of a
pneumatic cavity in a dorsal rib of A. louisae
(Fig.9). Supersaurus provides unambiguous
evidence of pneumatized ribs (LOVELACE et al.,
2003). If MARSH (1896) and GILMORE (1936) are
correct, then this condition may be
synapomorphic to apatosaurines. Alternately,
Fig.6- Caudal vertebrae of Diplodocus, Supersaurus, and Apatosaurus shown to demonstrate differences in the height of
the neural spine relative to the centra. Note also the distally expanded neural spines of both Supersaurus and Apatosaurus;
in lateral view the keel is apparent as well.
amongst diplodocids pneumatic ribs may be an
apomorphic condition of Supersaurus.
The length of the longest preserved rib is
305cm. Even on an animal as large as
Supersaurus this is relatively long. This results
in a deep thoracic cavity (Fig.7). This is at odds
with Barosaurus and Diplodocus, but similar to
Apatosaurus (Figs.7-8). The robust, laterally
expansive distal portions of the ribs are more
similar to Apatosaurus (GILMORE, 1936) than to
diplodocines, even in large diplodocine taxa like
Pectoral girdle – The only known pectoral
elements for Supersaurus are the
scapulocoracoids from Dry Mesa (Fig.10).
Scapulocoracoid BYU 9025 demonstrates a
deltoid ridge that is perpendicular to the
acromian ridge and the scapular blade is one-
half the entire length of the scapulocoracoid.
Both of these features are seen in Apatosaurus
but not in Diplodocus or Barosaurus, which have
relatively short scapular blades, and an acute
angle between the deltoid ridge and the acromian
ridge. This angle is much stronger in Barosaurus
than it is in Diplodocus. The apatosaurine nature
of the scapulocoracoids further reinforces the
referral of BYU elements to the type scapula, as
well as our referral of WDC DMJ-021 to
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Fig.7- Comparative skeletal reconstructions of Barosaurus lentus, Apatosaurus louisae, and Supersaurus vivianae to
the same scale.
Fig.8- Comparative skeletal reconstruction of Diplodocus carnegii, D. longus, and NMMNH 3690, “Seismosaurus”, to the
same scale.
Arq. Mus. Nac., Rio de Janeiro, v.65, n.4, p.527-544, out./dez.2007
Forelimbs – Because Barosaurus forelimbs are poorly
described, data from Apatosaurus and Diplodocus
(a good proxy for Barosaurus limb elements;
MCINTOSH, 2005) are used as a model for diplodocid
proportions; expected ratios were used for estimating
lengths for missing Supersaurus limb elements.
Using these predicted ranges, we can safely conclude
no additional Supersaurus forelimb elements were
recovered from the Dry Mesa Quarry. The ulna (BYU
13744) referred to the type specimen of Supersaurus
(CURTICE & STADTMAN, 2001) measures 1280mm, while
the maximum predicted value (relative to the
scapula) for the ulna is 1012mm, a 20% discrepancy.
Therefore the referral of BYU 13744 to Supersaurus
cannot be supported.
No humerus was located in the BYU collection that
matched the predicted range of humeral lengths.
BYU 17386 has been informally referred to
Fig.9- Pneumatic ribs described from the apatosaurines: A, Supersaurus (LOVELACE et al., 2003); B, Apatosaurus louisae
(GILMORE, 1936); and C, Apatosaurus excelsus (MARSH, 1896). p.f. = pneumatic foramen
Fig.10- Lateral view of Supersaurus right scapulacoracoid (BYU 9025).
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Supersaurus. Using the same methods as above,
a predicted range was generated. The length of
BYU 17386 is 1710mm, while the maximum
predicted value was 1424mm, a 17% discrepancy.
Pelvic girdle – CURTICE & STADTMAN (2001) referred
an articulated sacrum and right illium (BYU
13018), a left ischium (BYU 12555), and a right
pubis (BYU 12424) to Supersaurus. The pelvis
demonstrates dorsoventral shearing that
depressed the right illium ventrally and elevated
the left sacral ribs dorsally relative to the midline
of the sacral centra (Fig.11).
The ischium appears to be the match to the
element referred previously by JENSEN (1985),
whose referral was supported by CURTICE &
STADTMAN (2001). A partial ischium preserved with
WDC DMJ-021 is identical to both BYU ischia,
supporting referral of these specimens to
Supersaurus. Likewise, a pubic boot and partial
shaft of the left pubis (WDC DMJ-021-233) is
represented in the WDC specimen. The boot is very
similar to that preserved in the BYU pubis,
consistent with previous referrals (Fig.12).
Comparisons of the illium, pubes and ischia with
other diplodocids reveal additional apatosaurine
affinities, including a short, robust pubic
peduncle of the illium, and a large and fully
enclosed obturator foramen. In particular, the
robust margin surrounding the obturator
foramen contrasts with the condition in
Barosaurus, which is not completely enclosed
(MCINTOSH, 2005). Supersaurus and Apatosaurus
also share a large distal expansion of the ischia
(MCINTOSH, 1990).
Hind limbs – The tibiae and fibulae of both limbs
are present in the WDC specimen. Tibiae are
deformed, but exhibit and intermediate level of
robusticity, in between that of Apatosaurus and
Diplodocus. The tibia exhibits a large cnemial crest;
though less pronounced than in A. louisae (GILMORE,
1936) it is at least twice as long (proximodistally)
as Diplodocus carnegii (HATCHER, 1901). The distal
end of the tibia is also expanded mediolaterally,
similar to that seen in A. louisae (Fig.13).
The fibulae compare well with Apatosaurus,
including broad anteroposteriorly expanded
proximal and distal ends. The M. biceps femoris
scar is pronounced, as described for Apatosaurus
(GILMORE, 1936). This contrasts with the weakly
expanded proximal and distal ends of the tibia of
both Barosaurus (MCINTOSH, 2005) and Diplodocus
(HATCHER, 1901).
Fig.11- Right lateral (a) and posterior view (b) of Supersaurus partial sacrum and articulated right illium (BYU 13018)s.
Arq. Mus. Nac., Rio de Janeiro, v.65, n.4, p.527-544, out./dez.2007
The primary phylogenetic analysis (utilizing the
modified matrix of HARRIS & DODSON, 2004) resulted
in three equally parsimonious trees of 466 steps. The
resulting strict consensus tree (Fig.14) has a
Confidence Index of 62 and a Retention Index of 78.
The analysis recovered a monophyletic Apatosaurinae
consisting of Suuwassea as the sister taxon to
Apatosaurus + Supersaurus. Inclusion of Seismosaurus
in the analysis resulted in a sister-group relationship
between Seismosaurus and Diplodocus, with
Barosaurus as the most basal diplodocine. These
results are consistent with the apatosaurine axial
morphology of Suuwassea (HARRIS, 2006), and
corroborates the distinction of Supersaurus from
Barosaurus, Seismosaurus, and Diplodocus.
It is possible that some similarities between
Supersaurus and other apatosaurines result from a
size-coupled increase in robustness, but it is worth
noting that apatosaurine robustness does not
correlate with size, and large diplodocines like
Seismosaurus do not exhibit markedly more robust
pelvic or costal elements, making it unlikely that size
is obscuring the phylogenetic signal. Other characters
such as proximal centra that are heart-shaped in
cross-section, and paired ventral pneumatopores in
the cervical vertebrae are certainly decoupled from
size. Scoring Supersaurus into other published
analyses (e.g. UPCHURCH et al., 2004) also recovers a
monophyletic Apatosaurinae with Supersaurus
embedded in it (LOVELACE et al., 2005).
Recovery of Supersaurus and Suuwassea as non-
diplodocine diplodocids demonstrates greater
apatosaurine diversity than previously suspected.
Apatosaurines have not been reported outside of
North America, raising the biogeographic possibility
that apatosaurines may have been restricted to
North America.
While Seismosaurus was recovered as the sister taxa
to Diplodocus, it was identical to the scoring of
Diplodocus prior to the addition of our Character 1
(Appendix 1). It has since been discovered that the
hook-shaped distal expansion on the ischia of
Seismosaurus does not exist (LUCAS et al., 2006),
Fig.12- Left lateral view of Supersaurus left pubis BYU 12424 (a) and right lateral view of Supersaurus right ischium
BYU 12946 (b).
Arq. Mus. Nac., Rio de Janeiro, v.65, n.4, p.527-544, out./dez.2007
so Seismosaurus is once again indistinguishable from
Diplodocus in our analysis.
Examining descriptive osteology for Diplodocus
1932; MCINTOSH & CARPENTER, 1998), we concur with
CURTICE’s (1996) suggestion that the caudal vertebrae
of the type of Seismosaurus (NMMNH 3690) constitute
a nearly continuous series, instead of consisting of
major gaps as suggested by GILLETTE (1991). Following
GILLETTE’s (1991) numbering of the caudals would
require morphology not seen in any diplodocid,
including extremely elongate mid-caudal vertebrae
with hyper-developed mid-caudal neural spines, and
a continuation of the transverse processes far past
caudal vertebrae 15-18, the termination point in all
other diplodocid taxa (MCINTOSH, 2005).
Fig.13- Comparison of tibiae (upper row) and fibulae (lower row) of: A) Apatosaurus louisae (GILMORE, 1936), B) Supersaurus
vivianae (WDC DMJ-021), and C) Barosaurus lentus (MCINTOSH, 2005).
Arq. Mus. Nac., Rio de Janeiro, v.65, n.4, p.527-544, out./dez.2007
Fig.14- Strict consensus tree resulting from the addition of Supersaurus and “Seismosaurus” into a modified matrix from
Interpreting the caudal series of Seismosaurus
as a single series of the 22 anterior-most caudals
(with perhaps one missing), the morphology is
consistent with other diplodocines, and is nearly
identical with that described for Diplodocus
longus (e.g. OSBORN, 1899). The maximum centra
length reported by GILLETTE (1991) is 350mm.
When compared to the largest caudal vertebrae
of Diplodocus longus (325mm; GILMORE, 1932)
there is only a 2.5cm difference (under 10%).
The remaining caudals are within the range of mid-
caudal vertebral lengths reported for Diplodocus
longus by GILMORE (1932).
The phylogenetic placement of Seismosaurus
reinforces the osteological finding that Supersaurus
is distinct from Seismosaurus. Based on the
extremely similar morphology of the Seismosaurus
axial and pelvic morphology to specimens of
Diplodocus, we refer NMMNH 3690 to Diplodocus,
and most likely to D. longus.
Arq. Mus. Nac., Rio de Janeiro, v.65, n.4, p.527-544, out./dez.2007
While length and mass estimates of extinct animals
have utility for constructing paleo-ecological models,
there can be little doubt that public fascination is
in part responsible for the numerous size estimates
in the scientific literature (COLBERT, 1962; GILLETTE,
1991, 1994; PAUL, 1997). Widely varying estimates
suggest that more rigor (or perhaps restraint) needs
to be applied.
Between the WDC and BYU specimens of
Supersaurus, most of the presacral axial column
is known, and the caudal series is well represented.
Using apatosaurine proportions to fill in the
missing caudal elements, we reconstruct a length
of 33-34m along the axial column for the known
specimens of Supersaurus (Fig.7), with the BYU
specimen being marginally larger.
In comparison, using the proportions of Diplodocus
longus, we estimate a length of 30m for the NMMNH
“seismosaur” specimen (Fig.8). While within the low
end of the size estimate provided by D. Gillette (28-
36m, 1991), it is far less than the 39-52m length
considered “more probable” at the time.
The literature is littered with attempts to estimate
the mass of the largest dinosaurs (COLBERT, 1962;
ANDERSON, 1989; GILLETTE, 1994; PAUL, 1997). While
many studies have used long-bone circumference to
estimate mass, we agree with ANDERSON (1989) and
PAUL (1997) that variation in the strength index of
the femora of extant tetrapods is too great to produce
anything more than general ranges. For greater
precision we worked with a paleo-life artist to
construct a sculpted model based on the proportions
of Supersaurus for volumetric measurement (Fig.15).
Water-displacement measurements where compared
against a 3D laser scan of the model to ensure
accuracy of measurement. Assuming a specific
gravity of 0.8 (WEDEL, 2004) provides an estimate
35-40 tons in life.
While the more gracile Seismosaurus likely massed
significantly less, other sauropods such as
Argentinosaurus clearly achieved much greater bulk.
WDC DMJ-021 is the second and most complete
specimen of Supersaurus to date. Because only a
single individual was found in the quarry, it serves
as a test against elements referred to the type
individual found in the Dry Mesa quarry.
With the additional information provided by WDC
DMJ-021, enough morphological differences exist
to distinguish Supersaurus from other diplodocids.
Previously ascribed similarities to Barosaurus or
Seismosaurus” are based upon material
inaccurately referred to Supersaurus, or to gross
similarities in neck elongation or overall size.
Adding Supersaurus to existing phylogenetic
analyses recovers a more diverse Apatosaurinae
than previously thought. Both Suuwassea and
Supersaurus are found to be more closely related
to Apatosaurus than to other sauropods. At this
point apatosaurines appear to be an indigenous
clade of North American diplodocid sauropods.
Fig.15- Multiple view skeletal reconstruction used to guide the construction of a physical model for volumetric measurements
used in mass estimate.
Arq. Mus. Nac., Rio de Janeiro, v.65, n.4, p.527-544, out./dez.2007
Greater resolution of diplodocid phylogenetics will
likely require a reassessment of individual species
of Apatosaurus and Diplodocus.Seismosaurus’ can
be referred to the latter, specifically to D. longus.
Supersaurus was neither the heaviest nor the
longest sauropod, although it is well enough known
to place confidence in its estimated length of 33-
34 meters, and mass of 35-40 tons.
We would like to firstly thank the landowners who
wish to remain anonymous for donating the
supersaur specimen to the Big Horn Basin
Foundation. Secondly we would like to thank the
volunteers who helped excavate and prepare this
specimen over the last 10 years. Also we would
like to thank two anonymous reviewers. The
manuscript was greatly improved; thanks to your
helpful comments. Special thanks go to Burkhard
Pohl, the University of Wyoming, Casper College,
the Big Horn Basin Foundation for financial and
institutional assistance with this project, and John
Rader for his wonderful sculpture.
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235 236 237 238 235 236 237 238
Prosauropoda ? ? ? ?
Jobaria ? ? ? ?
Theropoda ? ? ? ?
Malawisaurus ? ? ? ?
Vulcanodon ? ? ? ?
Nigersaurus ? ? ? ?
Barapasaurus ? ? ? ?
Rayososaurus ? ? ? ?
Omeisaurus ? ? ? ?
Rebbachisaurus ? ? ? ?
Shunosaurus ? ? ? ?
Alamosaurus ? ? ? ?
Patagosaurus ? ? ? ?
Nemegtosaurus ? ? ? ?
Mamenchisaurus ? ? ? ?
Neuquensaurus ? ? ? ?
Apatosaurus 0 0 0 0
Opisthocoelicaudia ? ? ? ?
Barosaurus 0 1 0 1
Rapetosaurus ? ? ? ?
Brachiosaurus ? ? ? ?
Saltasaurus ? ? ? ?
Camarasaurus ? ? ? ?
‘T.’ colberti ? ? ? ?
Dicraeosaurus 0 1 0 0
Supersaurus 0 0 0 0
Diplodocus 0 1 1 1
Suuwassea ? ? ? ?
Haplocanthosaurus ? ? ? ?
Seismosaurus 1 1 1 1
Amargasaurus ? ? ? ?
Losillasaurus ? ? ? ?
Euhelopus ? ? ? ?
#235. Posteriodorsal expansion of distal ischium: absent (0); present (1). This character was needed to
separate Seismosaurus from Diplodocus, otherwise they are scored the same. It has been suggested that
might in fact be either a new species of Diplodocus, or larger specimen of D. longus (Fig.12).
#236. Ratio of neural spine height to centrum height (first caudal vertebrae): less than 2 (0); greater
than 2 (1). The height of the neural spine is measured from the top of the centrum to the top of the
neural spine. The neural spines of both Apatosaurus and Supersaurus are relatively shorter than those
seen in Dicreaosaurus, Barosaurus, and Diplodocus (Fig.6).
#237. Anterior caudal neural spines bifed: absent (0); present (1). Bifed neural spines are present in the
apex of the neural spines in Diplodocus and Seismosaurus. Supersaurus exhibits a wide rectangular
distal neural spine (Fig.6).
#238. Location of hyposphene on posterior dorsal vertebrae: less than one half total height of vertebra (0);
greater or equal to one half total height of vertebra. The neural arches of the diplodocines are taller than in
either Supersaurus or Apatosaurus, making the neural spines relatively shorter in the diplodocines (Fig.5).
... The ventral margin of the anterior cotyle, although partial, preserves a small chevron facet (Fig. 5A). The preserved lateral surface of the centrum is convex and bears a lateral foramen immediately ventral to the neural arch, a feature present in anterior caudals of most diplodocids 23,40,43 (Fig. 5B). The lateral surface, however, does not bear any ridges, similar to Amargatitanis 11 . ...
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The Early Jurassic and Cretaceous deposits of India are known for their diverse sauropod fauna, while little is known from the Middle and Late Jurassic. Here we report the first ever remains of a dicraeosaurid sauropod from India, Tharosaurus indicus gen. et sp. nov., from the Middle Jurassic (early–middle Bathonian) strata of Jaisalmer Basin, western India. Known from elements of the axial skeleton, the new taxon is phylogenetically among the earlier-diverging dicraeosaurids, and its stratigraphic age makes it the earliest known diplodocoid globally. Palaeobiogeographic considerations of Tharosaurus, seen in conjunction with the other Indian Jurassic sauropods, suggest that the new Indian taxon is a relic of a lineage that originated in India and underwent rapid dispersal across the rest of Pangaea. Here we emphasize the importance of Gondwanan India in tracing the origin and early evolutionary history of neosauropod dinosaurs.
... CDF and POCDF), and that the pneumatic excavations pierce the centrum as invasive foramina, as originally noted by Russell and Zheng (1993). Deep paramedian fossae on the ventral surface of postaxial cervical vertebrae occur in Haplocanthosaurus and some flagellicaudatans (Tschopp et al., 2015;Whitlock, 2011), and in both Supersaurus (Lovelace et al., 2007) and Galeamopus (Tschopp & Mateus, 2017) these fossae have been noted to contain invasive pneumatic foramina ('pneumatopores'). Cervical 7 of Datousaurus also bears deep, anteriorly positioned paramedian ventral fossae (Peng et al., 2005, fig. ...
The sauropod genus Mamenchisaurus, from the Late Jurassic–Early Cretaceous of East Asia, has a convoluted taxonomic history. Although included in the first cladistic analysis of sauropods, only recently has the monophyly of Mamenchisaurus, and the anatomical diversity of the many penecontemporaneous East Asian eusauropods, been evaluated critically. Here, we re-describe the holotype and only specimen of M. sinocanadorum. Although the original diagnosis is no longer adequate, we identify several autapomorphies that support the validity of this species, including an elongate external mandibular fenestra and distinctive pneumatic structures on the cervical centra. We incorporate new data into a phylogenetic character matrix that also includes Bellusaurus and Daanosaurus, both of which are known only from juvenile material and are often hypothesized to be neosauropods (or close relatives thereof). We recover all species of Mamenchisaurus as part of a radiation of predominantly Middle–Late Jurassic East Asian eusauropods, but the genus is non-monophyletic, underscoring the need for further systematic revision of mamenchisaurid taxonomy. Analyses that score ontogenetically variable characters ambiguously recover Bellusaurus and Daanosaurus as juvenile mamenchisaurids, a hypothesis supported by several features that are unique to mamenchisaurids or exhibit little homoplasy, including anteriorly bifurcate cervical ribs. Finally, computed-tomography reveals extensive vertebral pneumaticity in M. sinocanadorum that is comparable to that of the largest sauropods, and updated scaling analyses imply a neck over 14 m long, rivalling estimates for other exceptionally long-necked sauropods. Previous work has suggested that the elongated cervical ribs of particularly long-necked sauropods such as M. sinocanadorum stabilized the neck by limiting its mobility. Given that extent of pneumaticity responds dynamically to a bone’s habitual loading, we propose that long cervical ribs – and other structural modifications that limited flexibility – promoted the evolution of increasingly long necks by producing a more predictable biomechanical milieu amenable to increased pneumatization.
... In dorsal view ( Figure 6B), the bone is sub-rectangular, wider than long due to the lateral expansion of the distal portions of spdl, as seen in posterior dorsal vertebra of Rebbachisaurus MNHN-MRS-2000 (Wilson and Allain 2015). In anterior view, the dorsal surface is medially concave, whereas the lateral edges are convex and slightly prominent, which is a condition also present in the posterior dorsal vertebrae of the indeterminate rebbachisaurid MMCh-PV-49 and several flagellicaudatans, such as Apatosaurus, Barosaurus, Diplodocus, and Supersaurus (Marsh 1877;1878, p. 1890Lull 1919;Janensch 1914;Jensen 1985;Lovelace et al. 2007;Haluza et al. 2012). The prsl is slender ventrally and transversely expanded at the distal half, especially close to the apical portion of the neural spine. ...
The Lohan Cura Formation (Albian) at the Cerro de los Leones locality (Neuquén Province, Patagonia, Argentina) yielded several fossil materials, especially sauropod specimens. Among these, Agustinia ligabuei includes postcranial elements of a single individual, with widely debated taxonomy and phylogeny. Here, we provide an extended osteological description and illustrations of the axial and appendicular elements of Agustinia, as well as a revised diagnosis. Moreover, the phylogenetic analysis including a new combination of morphological features recognises Agustinia as a basal Rebbachisauridae, closely related with other South American rebbachisaurids. Our results suggest a more diversified sauropod fauna in the Neuquén Basin, where different members of both neosauropod lineages (i.e. Macronaria and Diplodocoidea) survived in the same region during the Albian age. The reassessment of Agustinia as a basal rebbachisaurid improves our knowledge about the early stages of evolutionary history of Rebbachisauridae, adding new information on the morphological and taxonomic diversification of the clade during the Early Cretaceous of southwestern Gondwana.
... more recent reconstructions corresponding to D GA /H A of 1.0 or less, especially in subadults and juveniles due to their relatively longer limbs (Lovelace et al., 2007;Schwarz, Ikejiri, et al., 2007b;Stevens, 2013;Stevens et al., 2016;Woodruff & Foster, 2017;Woodruff et al., 2018). Here we assume D GA /H A = 1.0 ± 0.1. ...
Full-text available
The gleno-acetabular distance D GA , a conventional proxy for the size of a quadrupedal trackmaker, is often estimated as the distance GA between the midpoint between a left and right pair of pes tracks and the midpoint between a selected pair of left and right manus tracks. While frequently used to estimate trackmaker size from fossil trackways, the relationship between GA and D GA depends upon the gait (which is unknown for extinct trackmakers), and is subject to multiple additional sources of uncertainty including which specific pair of manus tracks to associate with a given pair of pes tracks. Here a generalization is introduced, termed coupling length, which does not require any presumption about trackmaker gait of the degree of overstepping. On the contrary, a systematic analysis of a trackway in terms of coupling length can permit estimation of both the size and the gait with which the trackmaker progressed. Coupling length can be computed at successive points along a trackway, allowing exploration of a range of hypothetical gaits and body sizes for the trackmaker responsible. A fitness function quantifying persistent variation in coupling length along a trackway is used to indicate whether a given trackway could have been created by a fairly consistent gait, and if so, a range of high-fitness solution gaits and their associated D GA . The method was applied to selected quasi-regular sauropod trackways and a solution found for a narrow range of gaits with limb phase of about 0.3 and D GA = 1.6 ± 0.2 m. This is the first estimation of sauropod trackmaker gait, and introduces a novel method by which irregularity along a trackway is used as a source of information to constrain inferences of trackmaker behavior. The computed D GA for this sauropod suggests significantly smaller trackmakers than conventional estimations based on track dimensions and hip height estimates. Size estimation by this approach offers greatly reduced uncertainty compared to conventional estimates.
... The older specimen numbers are mentioned under "further info" (see below). There are also cases, where specimens got renumbered while remaining in the same institution (e.g., the holotype scapulacoracoid of the diplodocid Supersaurus; Jensen, 1985;Curtice & Stadtman, 2001;Lovelace et al., 2007); we also recorded the old specimen numbers in the column "further info" here. ...
Full-text available
The Morrison Formation has been explored for dinosaurs for more than 150 years, often specifically for large sauropod skeletons curators wanted to mount as attractions in their museum exhibits around the world. Several long-term campaigns to the Jurassic West of the United States produced hundreds of specimens, ranging from isolated, fragmentary bones to nearly complete skeletons of these enormous herbivorous animals. Given the sheer number of specimens, keeping track of what is housed in which institution is paramount to study variability, taxonomy, and consequently geographic and temporal distribution of the various species and genera recognized from the Morrison Formation. In an attempt to facilitate these studies, we have compiled an online spreadsheet intended to combine all the available information on sauropod specimens from collection databases, published literature, and personal observations. These include lists of contents of the specimens, in what institution the material is housed, references mentioning, describing, figuring, providing measurements and/or 3D scans, locality data and stratigraphy, as well as other potentially useful data for research purposes. The spreadsheet is openly accessible, but editing is currently restricted to the authors of this study, in order to ensure high-quality data curation to keep the file as useful as possible.
... For example, this cleft is present up to, and including, dorsal vertebra 8 (of 9) in Barosaurus lentus [76], and dorsal vertebra 9 (of 10) in Apatosaurus louisae [56] and Diplodocus carnegii [30] (figure 6). By contrast, no cleft is present in the posterior dorsal neural spines of Supersaurus vivianae [15]. ...
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Sauropod dinosaurs were an abundant and diverse component of the Upper Jurassic Morrison Formation of the USA, with 24 currently recognized species. However, some authors consider this high diversity to have been ecologically unviable and the validity of some species has been questioned, with suggestions that they represent growth series (ontogimorphs) of other species. Under this scenario, high sauropod diversity in the Late Jurassic of North America is greatly overestimated. One putative ontogimorph is the enigmatic diplodocoid Amphicoelias altus , which has been suggested to be synonymous with Diplodocus . Given that Amphicoelias was named first, it has priority and thus Diplodocus would become its junior synonym. Here, we provide a detailed re-description of A. altus in which we restrict it to the holotype individual and support its validity, based on three autapomorphies. Constraint analyses demonstrate that its phylogenetic position within Diplodocoidea is labile, but it seems unlikely that Amphicoelias is synonymous with Diplodocus . As such, our re-evaluation also leads us to retain Diplodocus as a distinct genus. There is no evidence to support the view that any of the currently recognized Morrison sauropod species are ontogimorphs. Available data indicate that sauropod anatomy did not dramatically alter once individuals approached maturity. Furthermore, subadult sauropod individuals are not prone to stemward slippage in phylogenetic analyses, casting doubt on the possibility that their taxonomic affinities are substantially misinterpreted. An anatomical feature can have both an ontogenetic and phylogenetic signature, but the former does not outweigh the latter when other characters overwhelmingly support the affinities of a taxon. Many Morrison Formation sauropods were spatio-temporally and/or ecologically separated from one another. Combined with the biases that cloud our reading of the fossil record, we contend that the number of sauropod dinosaur species in the Morrison Formation is currently likely to be underestimated, not overestimated.
... At a point in the Late Triassic the sauropod lineage first appeared from within Sauropodomorpha (Cooper 1984;Upchurch 1998;Wilson and Sereno 1998;Yates et al. 2010;McPhee et al. 2014McPhee et al. , 2015McPhee et al. , 2017; this group went on to give rise to a large number of truly remarkable taxa in the later stages of the Jurassic and the Cretaceous, including the well-known diplodocids, such as Apatosaurus ajax, Brontosaurus excelsus and Diplodocus carnegii, and macronarians, such as Argentinosaurus huinculensis, Brachiosaurus altithorax and Giraffatitan brancai. Members of Sauropoda represent some of the largest land animals ever to have existed, with some genera estimated have been in excess of 120 metric tonnes in mass and 30-35 metres in length (Mazetta et al. 2004;Lovelace et al. 2007;Sander et al. 2011). ...
Tail elongation is a trait common to many sauropod dinosaurs. In certain members of Diplodocidae, for example, the total caudal vertebrae count is as high as 70 to 80 bones, making a total estimated tail length for mature animals that is in excess of 10 metres. A number of competing hypotheses have been suggested to explain the function of this ‘hyper-elongate’ tail including use as a counterbalance, use as a defensive weapon, use as a sonic-boom-generating ‘bull-whip’ or use as a feature for sexual display. Here, a new hypothesis is presented for the function of sauropods’ hyper-elongate tails – herding co-ordination. Many sauropods are known, from multiple independent lines of evidence, to have been herding animals that moved in large groups over wide ranges; it is proposed that the elongation of the tails in many of the more massive sauropod lineages may have evolved to allow for simple and efficient communication between individuals via near continuous animal-to-animal contact during herd movement and migration. This contact, it is suggested, would have facilitated speedier, more compacted and more efficient mass movement of the animals as a group, and reduced the need for continual slowing and stopping to maintain herd formation. Institutional abbreviations AMNH: American Museum of Natural History, New York, USA; CM: Carnegie Museum of Natural History, Pittsburgh, USA; HMN: Natural History Museum, Berlin, Germany; OMHN: Sam Noble Oklahoma Museum of Natural History, Oklahoma, USA
A fragmentary and the largest single bone element from the Lower Cretaceous Kanmon Group in Kyushu Island, southwestern Japan reported yet to date is described. This specimen has a fossa and lenticular foramen on its lateral surface and internal chambers of both large and small sizes. It was identified as the cervical vertebra of a titanosauriform sauropod dinosaur mainly based on such pneumatic structure. This specimen represents the first titanosauriform to be described from the Kanmon Group.
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The Upper Jurassic Morrison Formation classically represents the “Golden Age” of sauropods, and the Morrison Formation is reported to have yielded 13 genera and 24 species of sauropods. This incredible diversity has produced numerous theories attempting to reconcile the co-occurrence of such large, and similar taxa. Previously, a comparably high diversity has been proposed for the Late Cretaceous Hell Creek Formation of North America – possibly comprising nearly three dozen species from over 20 genera of ankylosaura, caenagnathids, ceratopsians, dromaeosaurids, hadrosaurs, ornithomimids, pachycephalosaurs, thescelosaurs, and tyrannosaurs. However, much of the morphologic variation previously ascribed to taxonomic differences has recently been shown to be a result of stratigraphy and/or ontogeny – resulting in this rich assemblage being downsized to 13 genera and 16 species. Whereas still rich in diversity, such factors have an immediate effect towards our reconstruction of true richness.Following the example of the Hell Creek Formation, we can investigate the ontogenetic and strati-graphic origin of possible diversity inflation in other formations, and within this study, apply it to the Morrison Formation. New dating techniques are resulting in finer temporal resolution, and are changing the temporal position of well-known quarries. Differences in body size and ontogenetic stages can also affect diversity estimates. Plotting body size stratigraphically, it initially appears that larger specimens (interpreted as different species) occur higher in the section. An increase in average body size may be a legitimate trend, but there are several specimens that counter this “rule” for many genera. Likewise, dramatic allometric ontogenetic trajectories have led to the erection of at least three diplodocid genera – Amphicoelias, Seismosaurus, and Suuwassea – and it is suspected that many more Morrison Formation “species” could alternatively be explained as ontogimorphs. We have a long way to go towards revealing the true nature of Morrison Formation sauropod diversity. Although dietary partitioning undoubtedly occurred at the level of both the species (e.g., Brachiosaurus vs. Diplodocus) and between ontogenetic stages, a base of 24 levels of co-occurring divisions seems unlikely. The Morrison Formation may have exhibited a sauropod-rich assemblage unlike any other in North America, and the implications of stratigraphy, ontogeny, and variation may be minor, yet these factors alter perceived “diversity.” True diversity will not be fully understood unless these factors are considered.
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Sauroposeidon proteles is a large brachiosaurid sauropod recently described from the Antlers Formation (Aptian-Albian) of southeastern Oklahoma. Sauroposeidon represents the culmination of brachiosaurid trends toward lengthening and lightening the neck, and its cervical vertebrae are characterized by extensive pneumatic structures. The elaboration of vertebral air sacs during sauropod evolution produced a variety of internal structure types. We propose a new classification system for this array of vertebral characters, using computed tomography (CT) of pneumatic internal structures. Comparisons with birds suggest that the vertebrae of sauropods were pneumatized by a complex system of air sacs in the thorax and abdomen. The presence of a thoraco-abdominal air sac system in sauropods would dramatically affect current estimates of mass, food intake, and respiratory requirements. Sauroposeidon was one of the last sauropods in the Early Cretaceous of North America; sauropods disappeared from the continent by the early Cenomanian. The demise of sauropods in the Early Cretaceous of North America predates significant radiations of angiosperms, so the decline and extinction of this dinosaur group cannot be linked to changes in flora.
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The holotype of the Late Jurassic sauropod dinosaur Seismosaurus hallorum consists of part of the thoracic and caudal vertebrae, most of the sacrum and pelvis, some ribs and chevrons and an incomplete femur. Reexamination of the holotype indicates that Seismosaurus hallorum differs little from Diplodocus, and none of the morphological differences are significant enough to justify a separate genus. Particularly important to this conclusion has been careful re-examination and further preparation of the ischium of the S. hallorum holotype, which indicates that the distal, hook-like process originally described was actually the tip of a vertebral neural spine and sandstone matrix adhering to the ischium. We consider Seismosaurus to be a junior subjective synonym of Diplodocus. We suggest that Diplodocus hallorum is also a junior subjective synonym of D. longus, but a careful taxonomic revision of the species of Diplodocus is needed to verify this suggestion.
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During deposition of the Upper Jurassic Morrison Formation, water that originated as precipitation in uplands to the west of the Western Interior depositional basin infiltrated regional aquifers that underlay the basin. This regional groundwater system delivered water into the otherwise dry continental interior basin where it discharged to form two major wetland/lacustrine successions. A freshwater carbonate wetland/lacustrine succession formed in the distal reaches of the basin, where regional groundwater discharged into the Denver–Julesburg Basin, which was a smaller structural basin within the more extensive Western Interior depositional basin. An alkaline–saline wetland/lacustrine complex (Lake T'oo'dichi') formed farther upstream, where shallower aquifers discharged into the San Juan/Paradox Basin, which was another small structural basin in the Western Interior depositional basin. These were both wetlands in the sense that groundwater was the major source of water. Input from surface and meteoric water was limited. In both basins, lacustrine conditions developed during episodes of increased input of surface water. Inclusion of wetlands in our interpretation of what had previously been considered largely lacustrine systems has important implications for paleohydrology and paleoclimatology.
Suuwassea emilieae is a recently described dinosaur taxon discovered in the Upper Jurassic Morrison Formation of the western United States and the only non-diplodocid flagellicaudatan (Dinosauria: Sauropoda) known from North America. It retains sauropod symplesiomorphies that are unexpected in a Late Jurassic taxon and thus sheds light on the evolutionary origins of the Flagellicaudata. Despite being comparatively small, the holotype of Suuwassea demonstrates hallmarks of relatively advanced age. A phylogenetic analysis of 30 taxa and 331 characters retains Suuwassea in a trichotomy with the Diplodocidae (Apatosaurus + (Diplodocus + Barosaurus)) and the Dicraeosauridae (Dicraeosaurus + Amargasaurus). This lack of resolution is probably due to a combination of missing data, character conflict and poor incorporation of specimens referred to diplodocid taxa that differ from their holotype specimens and species holotypes. Middle Jurassic palaeobiogeographical reconstructions conflict with the hypothetical distribution of flagellicaudatans in the Middle and Late Jurassic based on their phylogeny, implying that physical barriers, such as epeiric seas, were not responsible for limiting their initial radiation. The postparietal foramen shared by Suuwassea, Dicraeosaurus, Tornieria and Amargasaurus may correlate to preferred existence in near-shore, terrestrial environments.
A reassessment of Ultrasauros macintoshi
  • B D Stadtman
  • K L Curtice
CURTICE, B.D.; STADTMAN, K.L. & CURTICE, L.J., 1996. A reassessment of Ultrasauros macintoshi (Jensen, 1985). In: MORALES, M. (Ed.) The Continental Jurassic. Arizona: Museum of Northern Arizona Bulletin, 60:87-95.
Death of a dinosaur: a reevaluation of Ultrasauros macintoshi
  • B D Curtice
CURTICE, B.D. & CURTICE, L.J., 1996. Death of a dinosaur: a reevaluation of Ultrasauros macintoshi (Jensen 1985). Journal of Vertebrate Paleontology, 16:26A.